Improved wood-screw



WO OD SGREW. l

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UNITED STATES ATENT OFFICEO H. A. HARVEY, on NEW YORK, N. Y.

IMPROVED WOOD-SCREW.

,To aZZ whom it may concern:

Be it known that I, HAYWARD A. HAR- "VEY, of the city, county, and Stateof New York, have invented a new and useful Wood- Serew; and I do herebydeclare that the following, taken in connection with the drawings, is afull, clear, and exactdescrption thereof. a

In the drawings, Figure l is' a longitudinal central section through thescrew. Fig. 2 is an elevation' of' the head'and part of the shank, andFig. 3 is a plan of the lower side of the head.

Tle improved wood-screw herein descrihed has been devised i order to'secure a firmer hold in Wood, and to prevent in a measure, if

not Wlolly, all the tendeney of the screw to i The improvements arebs'ed upo'n'tle well known property of exjar out ot' the Wood'.

pansion of Wood after eompression.

The sc'ew is to be cut -in -any nsual or propermaehine, and the chaser sto be caused t) cut deeper than usnal at some part of the barrel of thesorew between the end of the 1 point and the place` Where the threadcomn'ences, as from A to B. [his operation will leave the pitch of thethread the sameas in the ordinary screw, but the thread willhavegreatest projection where the barrel of the screw is smallestindiameter; and also be thinner or cone more nearly to an edge at itspeiphery, as may be clearly see-n in the dran iugs. The barrel ofthe-screw will alsobe curvcd longitudinally; so that its diameter nearthe point is greater than its dianeter farther up the shank or barrel,and it is clear that it' the barrel were gripped at the small part thatit could not be pnlh'd out of the 'grippcr or grasping* body it' the'same were rigid, even-ifit had no thread. This longitudinal curve inthe barrel making the serew bnlbous--ointed, is theflfirstfeatnre of theinvention, and such bulbous-oointed screws nay be made witlfia thread ofVarying pro jection, as shown in the drawings,or with a thread which atall points projects the same distance from the barrcl. The former planis preferred.

The under side of the screw-head'represented in the drawings is cut intoteeth like ratchet-teeth, so that the screw can be turned easily in one'direction-wl'en in contact with Wood, and cannot be turned except Withdiffieulty in theother. These teeth are so formed With reference tothetwist of the screw-thread that their inclined faces compress the woodand pass over it when the screw is screwed in. When a screw such as isdescribed is forced into Wood, the latter will expand after the pointhas passed and grasp firnly 'around the small part of the barrel; and:when the thread draws the under sideof the head down upon the Wood theteeth will conpress the wote, and when the screw is hotne the woodexpanding Will` enter into the ratchet-teeth and prevent unscrewing,`except b breaking or cutting the Wood by the straight sides of the teetI prefer to 'make these screws with the entering part ot" the pointformed substantially 'as shown in the drawings, where the convolutionsot' the 'thread are represented as extending down the entvring part ofthe point; a

but stopping short oi' the extreniity thereof. By. this nethod of.construction a center point is forned which forns a guide, causing ,thescre'w't'o enter eXactly-a t the desired location, and also opens the'way so that the screw may be screwed in withcut the necessity of boringa ho'e, thereby causing the expanding Wood to grip firnly around thesmall part of the barrel. But the extrenity of the point may be of anyforn and the screw still remain bulbous-pointed so long as the barrel issmaller atsome part of its length than it is at another part betweenthat small part and the extrenity of the point, thereby bringing intoaction the expnding quality of the wood to secure the screw in placeirrespective of the hold of the threads.

l claim as of ny own in\'ention- 1. -A bulbous-pointed screW,substantially -such as -is hercin deseribed.

2. 'A bulbous-pointed screw with the thread projecting'unequally, sothat its periphery \villoccupy the same position that it 'wouldin ascrew ottheordinary form of barrel, 'substantially as described.

. 3. A bulbous-pointed ratchct'headed screw, constructed and having themode of operation herein set forth. 4

4. A bulbous-pointed serew provided with a center point without anythread on-the extremity thereot, substantially such as is hereinspecified.

In testimony whereof I have hereunto subscribed my name;

H. A. HARVEY.

